Process for volatilizing phosphorus and potash and for producing potashbearing phosphoric acid



Patented July 14, 1931 ROBERT D. PIKE, or OAKLAND, CALIEQRNIA m ra s 9ee -seam PH BH N POEASH N FOR a r-WW ere Barents "rnosrnoaic Adria NoDrawing.

This invention relates to the production of a potash bearing phosphoricacid and a. method of producing the same, preferably from phosphaterockand VVyomingite rock. i In southeastern Ida hooccur large quantities ofphosphate rock, and in southwestern 'Wyoming, about'twdhun'dred milesdistant occurs a" large tonnage of a"hig h'- grade Leucite rockcontaining about eleven per cent. (11%) ofKOfaridknown as w oniingite.These materials can be cheaply assembled at one point, and my presentnvention has for its object to provide a cheap process for producingfrom these a potashr rich phosphoric acidby volatilizatio'nin acoke-fired blast furnace. WVlie'reas myinvention is particularly adaptedto the treatment of Wyomingite and? phosphate rock, it will beunderstood that it nay equally well suited for use of other, similarfinateri als.

It is a well-known fact that it is ossible 'to volatilize"potash andphosphorus from mixes of phosphate rock, a potash-bearing silicate andcoke, in the electricfu'rnace. It has also been proposed (United StatesPatent Number 1,592,757), that a'colre-fire'd blast furnace be used forthis purpose, using a mixture of one partlphosphate rock and about twoparts of lVyoiningite,'with coke; but lit was found necessary, accordingto this patent, inorder to volatilize the potash from such a highlysiliceous mixture, to inject salt or calcium chlorid at the tuyeres.

There are several important objections to the last-named procedure, someof which are:

l. The formation of hydrochloric acid which passes over with the top gasfrom the'furnace;

2. The relatively large amount of slag which is formed per unit ofvaluable plant food volatilize dy' I 8. The highly siliceous nature ofthe slag,

my discovery A one part phosphate rock and seven tenths Applicationfiled ldfovember 14, 1927. Serial No. 233,325.

ence is objectionable in a potassium" ph'os- '1:

phate which will'u's'uallybe'sold on a chlorine-free basis. i

My invention consists in the substantially complete volatilization ofphosphorus'and potash from mixtures of phosphate rock andlvyom'ingite'or similar'materials in'a coke-fired 'blast'furnacewith 'a basic fiiii'dand with the production of afume Wlllbll will yield after oxidation andhumidification a which -is liquid under the usualco'nditions ofprecipitation Cottre'll 'precipi eator. "The present process 'ispreferably carried out in connection with my processfor volatilizingphosphorus, concurrently filed, be-

ingYSe rial Number 238,323, in which abla'st furnaceis employed whichuses'a' blast of air enriched with oxygen, and is based on that if Icharge a mixtureof to eight-tenths part vWVyomingite into such afurnace, together with from seventy to -eigh typoun'dsof coke to everyone hundred pounds of phosphate rock so charged, I can 5 effect asubstantially complete volatilization' of both the phosphorus and potashi n the charge withoutthe addition of'any chemicalsto promotevolatilizationof the latter.

As a result of such volatilizat'ion, the "fume which iscollected'in'tlie Cott'rell tor orby th rsuitable" means contains from.2' to .3 pounds -K per pound P 0 and is liquid as collected," and willflowout of 'thefcollector' or precipitator.

' The residual in the presence 'potash bearing phosphoric precipitagasis free from injurious corrosive substances, and may be employed as afuel gas. I have found that if the ratio of K 0 to P 0 goes much over .3to 1, the viscosity of the acid rapidly increases, so as to finallybecome unmanageable at ordinary temperatures of collection. Thephosphoric acid collected by my process, containing as it does from .2to .3 pounds K 0 per pound of P 0 is very valuable for preparingfertilizer com ounds, and my method of making it is so 0 cap as toconstitute a revolution in the art of producing phosphoric acid.

7 I have found that for the successful carrying out of my process in thecoke-fired blast furnace, the following general conditions have to beobserved:

1. The conditions in the hearth and bosh of the furnace must be stronglyreducing;

2. The charge should be so proportioned as to give in the slag aftercomplete elimination of K 0 and P 0 an excess of molecules of bases overmolecules of acids of from ten to thirty per cent. (considering aluminaas an acid) 3. The temperature of the slag should be from 1450 to 1500(1;

4. The slag should remain in the hearth of the furnace not less than twohours (and preferably over four hours), so as to give time for completeelimination of both the potash and phosphorus.

As a specific example of carrying out my process, I charge a blastfurnace with one part of phosphate rock and with eighttenths parts of\Vyomingite and .7 parts coke, giving a slag of about the followinganalysis:

Per cent S10 39. 7 A1 0 11. 9 CaO 43. 0 MgO 5. 4:

The furnace is blown with an oxygenated blast at 650 C. containing 30%of oxygen by weight. The slag is flushed every three to six hours. Theeliminations of phosphoric acid and potash are both above 85%, orsubstantially complete, and the ratio of K 0 to P 0 in the acid which iscollected from the top gas is about (after oxidation andhumidification), .29 to 1., which insures 'a good fluidity of the acidat the temperature of collection. It will be understood that the topgases as they issue from the top of the furnace, contain fumes of K 0and P 0 and of phosphorus. The latter has to be burned to P 0 in anysuitable manner by the admission of air. The air so admitted to burn thephosphorus will usually contain enough moisture for the formation ofortho phosphoric acid with the P 0 present; but if the air happens to beso dry as to be deficient in moisture for this purpose,

. the deficiency must be made up by introducing moisture into the gasesbefore they enter the precipitator.

It will be understood that many of the details concerning proportions,temperatures, etc., are subject to considerable variation withoutdeparting from the spirit of my invention, as disclosed in the appendedclalms.

Although I have specified the use of Wyomingite, it will be obvious thatany potashbearing silicate may be employed, and that if necessary thecomposition of the slag can be controlled by addition of other fluxingmaterials, as, for example, lime stone or dolomite.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. The process for the substantially complete volatilization ofphosphorus and potash from phosphate rock and \Vyomingite, whichconsists in charging into a coke-fired blast furnace one part ofphosphate rock with not more than eight-tenths part of \Vyomingite,together with the necessary amount of coke for furnishing heat and astrongly reducing condition in the hearth and bosh of the furnace,flushing the slag from the furnace after a sufiicient time of residenceto insure the substantially complete volatilization of phosphorus andpotash, adding air to the furnace top gases to oxidize all thephosphorus they contain to P 0 and sufficient moisture to convert P 0 toortho phosphoric acid, and collecting the phosphoric acid and potash.

2. The process of extracting potassium and phosphorus frompotassium-bearing and phosphorus-bearing rocks, which consists involatilizing the potassium and the phosphorus compounds by smelting therocks under reducing conditions in a coke fired blast furnace, thecharge being so proportioned that the slag contains an excess of basicmolecules over acid molecules, treating the gases produced by thesmelting op eration to cause the formation of an acid compound ofphosphorus and potassium, and thereafter recovering such compound fromthe gases in liquid form.

3. The process of extracting potassium and phosphorus frompotassium-bearing and phosphorus-bearing rocks, which consists involatilizing the potassium and the prosphorus compounds by smelting therocks under reducing conditions in a coke fired blast furnace, thecharge being so proportioned that the slag contains an excess of basicmolecules over acid molecules, oxidizing and humidifying the gases toform ortho phosphoric acid and potassium phosphate, and simultaneouslycollecting these compounds.

4t. The process for the substantially complete volatilization ofphosphorus and potash from phosphate rock and a potash-bearwhichconsists in charging into a coke-fired blast furnace one part ofphosphate rock with not more than eight-tenths part of potash-bearingsilicate, together with the necessary amount of coke for furnishingheatand a strongly reducing condition in the hearth and bosh of the furnace,flushing the slag from the furnace after a sufficient time of residenceto insure the substantially complete volatilization of phosphorus andpotash, and recovering said phosphorus and potash.

5. The process for the substantially complete volatilization ofphosphorus and potash from phosphate rock and vVyomingite, whichconsists in charging into a blast furnace fired with solid carbonaceousfuel, one part of phosphate rock with not more than eight-tenths part ofVyomingite, together with the necessary amount of solid carbonaceousfuel, for furnishing heat and a strongly reducing condition in thehearth and bosh of the furnace, flushing the slag from the furnace aftera sufficient time of residence to insure the substantially completevolatilization of phosphorus and potash, adding air to the furnace topgases to oxidize all the phosphorus they contain to P 0 and sufiicientmoisture to convert P 0 to ortho phosphoric acid, and collecting thephosphoric acid and potash.

6. The process of extracting potassium and phosphorus frompotassium-bearing and phosphorus-bearing rocks, which consists involatilizing the potassium and the phosphorus compounds by smelting therocks under reducing conditions in a blast furnace fired with solidcarbonaceous fuel, the charge being so proportioned that the slagcontains an excess of basic molecules over acid molecules, treating thegases produced by the smelting operation to cause the formation of anacid compound of phosphorus and potassium, and thereafter recoveringsuch compound from the gases in liquid form.

7. The process of extracting potassium and phosphorus frompotassium-bearing and phosphorus-bearing rocks, which consists involatilizing the potassium and the phosphorus compounds by smelting therocks under reducing conditions in a blast furnace fired with solidcarbonaceous fuel, the charge being so proportioned that the slagcontains an excess of basic molecules over acid molecules, oxidizing andhumidifying the gases to form ortho phosphoric acid and potassiumphosphate, and simultaneous- 1y collecting these compounds 8. Theprocess for the substantially complete volatilization of phosphorus andpotash from phosphate rock, and a potashbearing silicate, which consistsin charging into a blast furnace fired with solid caring silicate,

bonaceous fuels one part of phosphate rock v with not more thaneight-tenths part of potash-bearing silicate, together with thenecessary amount of solid carbonaceous fuel for furnishing heat and astrongly reducing condition in the hearth and bosh of the furnace,flushing the slag from the furnace after a suflicient time of residenceto insure the substantially complete volatilization of phosphorus andpotash, and recovering said phosphorus and potash.

ROBERT D. PIKE.

